Magnetic core assembly



Nov. 29, 1960 A. w. GELLERT ETAL 2,962,673

MAGNETIC coas: ASSEMBLY Filed May 16, 1957 v INVENTORS F/g, 4 ALVIN w. GELLERT JOHN PARSTORFER AGENT United States Patent MAGNETIC CORE ASSEMBLY Alvin W. Gellert, Bryn Mawr, and John Parstorfer, Philadelphia, Pa., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed May 16, 1957, Ser. No. 659,694

3 Claims. (Cl. 336-73) The present invention relates to magnetic cores and more particularly to a novel core assembly.

In magnetic core assemblies as heretofore fabricated considerable trouble has resulted from force fitting terminal pins through the core housing. This has occasionally resulted in a split housing due to overstressing of the housing material. Changes in the housing material used and permitting larger tolerances to overcome these difficulties only resulted in pin pull-outs during pin straightening operations, thereby rendering the unit inoperative. Also such pulling out develops cracks and other distortions in the housing making it necessary to discard the entire core assembly.

An object of the present invention is to provide a novel magnetic core assembly wherein the foregoing disadvantages are overcome.

Another object is to provide a magnetic core assembly wherein soldered joints of terminal wires are protected against re-melting during dip-soldering to secure the assembly to circuit panels.

Another object is to provide a magnetic core assembly wherein terminal wires are'permanently anchored into a molded housing body of insulating material, to thereby prevent them from being pulled out while being fabricated or while in use.

A further object is to provide a magnetic core unit wherein the core and associated windings are isolated from moisture.

Generally therefore in accordance with the foregoing objects of the invention there is provided a molded magnetic core assembly wherein terminal wires are interlocked in place and which includes means forming a loop axially traversing the core for core testing purposes. Furthermore the novel assembly provides an oversized housing capable of resisting strains and stresses usually present in the manipulation of soldered terminals.

In the accompanying drawings:

Fig. l is a sectional inverted view of the initial molding step in forming a core assembly in accordance with the invention;

Fig. 2 is a bottom view of the assembly after the initial molding;

Fig. 3 is a perspective View of the initial molded assembly with the core in place and core windings connected;

Fig. 4 is a section view similar to Fig. 1 and showing a subsequent molding operation resulting in a complete unit;

Fig. 5 is an elevational view of the complete core assembly showing the encapsulated parts in broken lines; and

Fig. 6 is a perspective view of one of the prepared terminal wires as an example of all.

Referring first to Fig. 5 of the drawings, it will be seen that the preferred form of the invention comprises the body or housing 7 including a molded base member 8 and a molded cap member 9. Encapsulated within the housing is a core 12 having wire wrappings 16 the ends 2,962,678 Patented Nov. 29, 1960 2 of which are connected to terminal ends of wires or pins 10, 13, and 14 having portions molded within the housing and opposite terminal portions extending from the base member 8.

Referring to Fig. 6, it is seen that the terminal wires 10 as prepared for molding respectively have a pinched or deformed portion 11 to serve as a means for anchoring each wire against pulling out of the molded base 8. These terminal wires 10 are, preferably, arranged in two rows of four spaced to receive the core 12 between them and with two terminal wires between these rows and straddling the core 12, all cooperating to substantially surround the core. For testing purposes there are two wires 13 and 14 to be connected at one end to form a single loop, as will be later explained, one such wire 13 projecting axial at both ends through the bore of the toroidal core 12 and the other wire 14 being parallel to the core in spaced relation. Both wires 13 and 14 are respectively axially offset bent as indicated at 15 to maintain true terminal row alignment for plug-in purposes. The array of terminal wires 10 are respectively bonded to the core windings 16 as by leads 16.

The assembly of wires, as seen in Fig. l, are positioned in the proper row arrangement by pressing one end of each into a ductile mold 17 such as rubber, having an upstanding projection 18 symmetrically located with respect to the terminal wires 10, 13 and 14, such projection 13 forming a circumferential channel 20 with anchoring portion of each terminal wireexcept 13- within such channel 20. With the array in place an electrically insulating nonmagnetic encapsulating material, such as fluid epoxy, is poured into the channel 20 to rise above the projection 13 sufficiently to for-m the base portion 8 of the housing. After the material has set, the base and embedded wires projecting from the opposite top and bottom surfaces thereof, is turned over and the core 12 seated in the cavity formed by the mold projection 18, which has a depth permitting approximately one half of the core to protrude as shown in Fig. 3. Also it should be noted that the bottom face of the base 8 has been formed during the molding operation with two ribs 22 and 23 paralleling the two rows of terminal wires. Preferably also the rib 22 has an offset extension 24 below the olfset portions of core loop wires 13 and 14 as a further reinforcement. The ribs may be formed by pressing a complementary formed mold member, not shown, into mold cavity 20 and against the encapsulating material before the latter has set. These ribs 22 and 23 serve to space the completed unit from a panel 25 or the like (Fig. 5) into which the prongs 26 are inserted for mounting as will be understood. By this spacing construction air is permitted to flow between the unit and the panel thus to prevent moisture due to condensation or otherwise from collecting between the unit and with the base. The ends of the loop wires 13 and 14 which protrude adjacent the seated core are bent into a side by side or overlapping relation as shown at 27 and 28 and then soldered into a bonded joint 29. This joint lies in close proximity to the protruding end of the core 12.

In order to form the cap member 9 of the unit, a second mold 30, having a properly shaped well 31, of area greater than the base member 8 is provided, and a liquid potting compound such as epoxy or the like, is now poured into a depth required for the thickness of the cap member. The molded base part 8 as shown in Fig. 3, is inverted and lowered into the body of material thereby causing the molding material to rise about the sides of the base until level with the top surface (as seen in Fig. 4) of portion 8, whereupon the material is allowed to set until ready for removal from the mold 30. When removed it appears as a sealed core assembly 7, as shown in Fig. 5, formed of portions 8 and 9, with the core 12 and terminal wires embedded therein except for the projecting wire ends 26 which serve as plug-in prongs or for other connections as the case may be.

It will now be apparent that a novel plug-in magnetic core assembly has been devised wherein the heretofore objectional pulling out of terminal wires has been eliminated so that the related cracking of the housing no longer takes place. Furthermore, by the increased length of the terminal wires and the added protecting body there is no possibility of re-melting internal soldered joints while dip-soldering the unit to a circuit board or panel. Also by providing means for spacing the unit from an associated part capillary and moisture infiltration to damage the embedded core and terminal wires is prevented.

What is claimed is:

1. A magnetic core assembly comprising, a molded base member of electrically insulating non-magnetic material having a centrally positioned cavity in one surface of opposite surfaces thereof, a plurality of terminal pins molded into base member, said pins being arranged around said cavity with terminal ends thereof extending from said opposite surfaces, a toroidal magnetic core positioned within said cavity, windings on said core, said windings having leads secured to the ends of said terminal pins extending from said one surface, a terminal pin extending through said base and the bore of said core,

another terminal pin extending through said base adjacent to the outer periphery of said core, said last two terminal pins having ends thereof secured together over said core to provide a conductive loop for said core, and a cap member of electrically insulating non-magnetic material molded over said one surface of said base member, said cap member cooperating with said base member to encapsulate the core and the terminal pins except for the terminal ends of said pins extending from the other of said opposite surfaces.

2. A magnetic core assembly comprising, a molded base member of electrically insulating non-magnetic material having a centrally positioned circular cavity in one surface of opposite surfaces thereof, a plurality of elongated terminal pins molded into said base member parallel to the axis of said circular cavity, said pins surrounding said cavity with terminal ends thereof extending from said one and the other of said opposing surfaces and having means to prevent displacement of said pins relative to said base member, a toroidal magnetic core para portion of said core extending from said one surface thereby to provide a test loop for said core, and a cap member of electrically insulating non-magnetic material molded over said one surface of said base member and extending around the sides of said base member between said opposing surfaces, said cap member cooperating with said base member to insulatingly encapsulate said core and that portion of said terminal pins within said base member and extending from said one surface leaving the other terminal ends of said pins exposed for connection to associated apparatus.

3. A magnetic core assembly comprising, a molded base member of electrically insulating non-magnetic material having a centrally positioned circular cavity in one surface of opposite surfaces thereof and ridges on the other of said opposite surfaces to provide clearance between said surface and associated apparatus when said base member is mounted thereon, a plurality of elongated terminal pins molded into base member parallel to the axis of said cavity, said pins surrounding said cavity with terminal ends thereof extending from said opposite surfaces and having deformed portions thereof embedded in said base member to prevent displacement of said pins relative thereto, a toroidal magnetic core partially positioned within said cavity and partially extending from said one surface, windings on said core, said windings having leads secured to the ends of said terminal pins extending from said one surface, a terminal pin extending through said base and the bore of said core, another terminal pin extending through said base adjacent the outer periphery of said core, said last two terminal pins having deformed portions in said ridges to prevent displacement of said pins relative to said base member, adjacent ends of said last mentioned two pins being secured together over a portion of the core extending from said one surface thereby to provide a test loop for said core, and a cap member of electrically insulating non-magnetic material molded over said one surface of said base member and extending around the sides of said base member between said opposite surfaces to an extent level with the other of said opposite surfaces, said cap member cooperating with said base member to insulatingly encapsulate said core and that portion of said terminal pins within said base and extending from said one surface leaving the other terminal ends of said pins exposed for connection to associated apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 1,763,115 Wermine June 10, 1930 2,091,234 Branson Aug. 24, 1937 2,168,382 Alden Aug. 8, 1939 2,707,272 Blitz Apr. 26, 1955 2,753,533 Houser July 3, 1956 2,785,383 Foster Mar. 12, 1957 2,836,805 Goldsmith May 27, 1958 

